Method for partially oxidizing methane



June s, 1941. P. NASHAN 2244x210 METHOD FOR PARTIALLY OXIDIZING METHANE `Iune 3, 1941. P. NAsHAN 2,244,210

METHOD FOR PARTIALLY OXIDIZING METHANE Filed oct. 4, 1938 2 rsheets-snm 2 Fig.3 l c Fig. r

j?? me@ af Patented June 3, 1941 UNITED STATES PATENT oFFlcl-z mmol) Fonllliy OXIDIZING Paul Nashan, Oberhausen-stormde, Germany ppuccaon october 4, 193s, serial No. 233,334

y lIn Germany October 11, 1937 lclaim.

It is the object of the present invention to provide a method for obtaining low molecular aliphatic aldehydes on a commercial scale, the aldehydes consisting primarily of acetaldehyde and/or formaldehyde. y

Several methods have been suggested for obtaining formaldehyde in particular by partially oxidizing gaseous or vaporous hydrocarbons in the presence of gaseous catalysts inthe form of small quantities of nitric oxides and of solid catalysts at temperatures between 500 and 700 C. Gases or vapors of the CH, CHn and Gummi: types were used as raw materials and organic acids were preferably obtained in addition to the above-mentioned oxidation product. It is not known.v however.- whether it was possible to develop the proposed methods beyond a certain experimental stage on a laboratory scale, as, when the experiments were carried out on a larger scale, it was found that it was not possible to control the reaction in the desired manner and if the repetition of the experiments on a commercial scale yielded any products at all they were neither economic nor uniform.

It has now been found that desired products.

such as low molecular aliphatic aldehydes and acetaldehyde or formaldehyde in particular can be uniformly produced from the gaseous and vaporous hydrocarbons of the CH., CnHm and CH2+z types when they are oxidized on a commercial scale, if in addition to the aforementioned steps the initial mixture is passed through a large number of tubes or ducts which are uniformly heated, possibly by means of a circulating heater. If necessary, the ducts or tubes are lined with the catalysts, further catalysts being possibly arranged in the ducts, or the ducts are themselves made of the catalysts. Oxides which are dicult to reduce, such as those of silicium, zinc, magnesium. titanium, cerium and similar metals, which can be used either alone or in combination, have proved to be particularly suitable catalysts for this purpose. Apart from these artificial materials natural rocks, such as granite, porphyry, mica, quartz and other natural products can with advantage be used as catalysts.

The reaction chamber is heated in a heater in which the individual ducts may be uniformly heated. The favorable eiect of the uniform heating of the furnace can be lincreased by circulating the heating gases, part of the burnt gases being, if necessary, removed and replaced by vfresh fuel gas which preferably heats the furnace by means of several burners. The heater is best arranged for regenerative or re- (Cl. 26o-604) cuperative heating, which offers the advantage that. the residual gas leaving the'reaction chamber of the heater can be used for heating the heater, so that the calorific value ofthe residual gas is utilized.

'Ihe method according to the invention is explained by the accompanying drawings- Fig. 1 being a vertical section through a reaction heater along the line A-A in Fig. 2,

Fig. 2 a vertical section along the line B-B in Fig. 1,

Fig. 3 a longitudinal section with circulating heating,

Fig. 4 a longitudinal section along th'e line C-C in Fig. 5 through a heater with regenerative heating, and

Fig. 5 a section along the line partially shown.

a is the furnace of the heater withthe burners b and the flues c. 4 divided into individual ducts d and so arranged in the heating zone that the substances participating in the reaction are uniformly and similarlyheated. As far as the ducts d are made through a heater of metallic materials their inner walls are lined with the .catalyst materials. 'Ihe walls of the ducts d can, however, themselves consist of the catalyst materials and catalyst materials may also be arranged inside the ducts.

In the reaction heater according to Figs. 1l

and 2 the heating gases coming from the furnace a pass round the reaction ducts d, throughv the ilues c and out of the heater as indicated by the arrows. The air and fuel pipes for the burners b are marked land lc respectively.

According to Fig. 3 fans e orvblowers for circulating the heating gases are arranged in front of the heating ilues. Before the heating gases re-enter the furnace part of them is led olf and leaves the heater through thev outlet pipe f, which is equipped with a control ap g. h indicates the peep holes.

Figs. 4 and 5 show a heater with regenerative heating. 'I'he heating gases are passed alternatively through a part of the. regenerative chambers i in order to ensure utilization of -the waste heat within the heater itself and the preheating of the air and/or gases for combustion in the other part of the regenerativel chambers. This makes it possible to burn gases with little heat content in the heater, to which in the present case can be added the out of the reaction ducts. k is the gas feed main and t the air pipe controlled by means of two- D-n in Fig.. 4,-

The reaction chamber is residual gases passing` way nap valves which, though not shown, are sumciently wellfknown.

Example.-In order to produce formaldehyde from methane a mixture of 49.8% by vol. of a gas separated from coke-oven gas containing 41% by vol. of methane as reaction gas. 50% by vol. of air and 0.2% by vol. oi.' nitric oxides (referred to NO) as catalyst is passed at a rate of more than '15 cm. per second through the re'- action ducts d. which are heated to a temperature of 620 C. The reaction ducts were lined and charged with solid catalyst material, the catalyst bodies consisting of puried clay mixed with 10% of zinc-oxide. The reaction gases were circulated. The yield was 560 grammes of (100%) formaldehyde per cu. m. of methane introduced into the reaction chamber. The residual gases passing out of the cycle were used for heating the heater, I

Besides-dividing the reaction chamber into a number of tubes or ducts as explained and passing the substances participating in the reaction through these tubes or ducts it is, of course, also possible if the reaction chamber isarranged accordingly. to pass the heating gases through the tubes or ducts and the reaction mixture round the tubes or ducts. The solid catalysts are then rrtiged around the outside of the tubes or Various changes in the steps of my method may be made by those skilled in the art without departing from the spirit of my invention as claimed.

What I claim is:

A commercial process for preparing a low molecular aliphatic aldehyde consisting in uniformly heating a mixture consisting of 49.8% by volume of a gas separated from coke over gas containing 41% by volume of methane, 50% air and 0.2% nitric oxides to a temperature of from 500 to '700 C., by passing the mixture in the presence of solid catalysts through a closed passage in a uniform heating zone.

PAUL NASHAN. 

